Flame-resistant hydrocarbon polymers



United States Patent 3,449,308 FLAME-RESISTANT HYDROCARBON POLYMERSPhilip Strnbing Blatz, Wilmington, Del., assignor to E. L du Pont deNemonrs and Company, Wilmington, Del., a corporation of Delaware NoDrawing. Continuation-impart of application Ser. No. 439,961, Mar. 15,1965. This application Jan. 18, 1966, Ser. No. 521,428

Int. Cl. C08f 27/08; C091: 3/28 U.S. Cl. 260-381 6 Claims ABSTRACT OFTHE DISCLOSURE tached to the olefin polymer by an uninterrupted carbonto carbon linkage.

This invention relates to flame-resistant polymers which aresubstantially hydrocarbon in nature. This application is acontinuation-in-part of application Ser. No. 439,961, filed Mar. 15,1965 and now abandoned, which is a continuation-in-part of Ser. No.167,934, filed Jan. 22, 1962, now abandoned.

The present invention is realized by chemically bonding phosphorus to asubstantially olefinic hydrocarbon polymer so as to produce thestructure C-NP with the carbon atom of the structure being bonded to thepolymer by a carbon-carbon linkage in the main chain or in a side chainso long as the attachment is through an uninterrupted sequence ofcarbon-carbon bonds.

The --CN--P linkage may be introduced by postreacting with asubstantially hydrocarbon copolymer prepared, usually by free-radicaltechniques, from a mono-aolefinic hydrocarbon having the structure CHCHR wherein R is selected from the group consisting of hydrogen andalkyl and alkaryl radicals having 1 to 16 carbon atoms, and amonoethylenically unsaturated comonomer selected from the groupconsisting of alkenoic and alkenedioic acids, alkenetricarboxylic acidsand methylene alkanedioic acids having 3 to 18 carbon atoms, and alkenylamides having 2 to 20 carbon atoms. The alkenyl amides have the formulawherein R and R are selected from the class consisting of hydrogen andalkyl groups having 1 to 4 carbon atoms. Examples of thesemonoethylenically unsaturated comonomers are acrylic acid, methacrylicacid, fumaric acid, maleic acid, itaconic acid, aconitic acid,acrylamide, methacrylamide, N-methyl acrylamide, N-methyl methacrylamideand the like. The preferred comonomers are acrylamide, methacrylamide,acrylic acid and methacrylic acid. Reduction products of the copolymerprepared from the above-described alkenyl amides are also operable.These reduction products may be prepared by known methods, e.g., byreacting the copolymer with lithium aluminum hydride or hydrogen with apalladium on carbon catalyst. In the substantially hydrocarboncopolymers, the amount of bound comonomer is limited to the range 0.2 to13 mole percent. To minimize the deleterious effects which thecomonomers exert on some properties, especially molecular weight, thecomonomer concentration most often is limited to a maximum of 4 molepercent.

Prior to introduction of the -C--NP linkage into the copolymer describedabove, the acid groups of the copolymer are converted to thecorresponding acid halide by conventional methods. The resulting acidhalide copolymer is then reacted with a compound having the generalformulae wherein X is selected from the class consisting of hydrogen, R,OR, NHR

and NH and Y is selected from the class consisting of R, OR, NHR, and

wherein R is an alkyl, aryl or aralkyl group having 1 to 18 carbonatoms, to produce the --CN-P linkage.

Examples of such phosphorus amides are CHz-O O NH:

cacyar 0 CiHs wherein X is selected from the group consisting ofhydrogen, R, OR, NHR and and Y is selected from the group consisting ofchlorine, R, OR, NHR and wherein R is defined as above. Examples ofthese phosphorus halides are P-Cl Regardless of the method ofintroducing the flameproofing agent, the substantially olefinichydrocarbon polymer usually may have bound thereto up to 4 mole percentphosphorus, although as little as about 0.1 mole percent sometimes willsuffice. The flame-resistant product should contain at least onephosphorus atom per 1000 carbon atoms of the substantially hydrocarbonpolymer. The bound phosphorus usually does not exceed 5 mole percent,and preferably 2.5 mole percent of the polymer to be made flameproof soas to minimize alteration of its base properties. In addition, thephosphorus should be uniformly dispersed throughout the polymer so thatthe maximum flame-resistance may be obtained.

The flame-resistant products prepared by the aforementioned techniquesmay be dissolved and reprecipitated, or, alternately, may be extractedor fractionated using appropriate polymer solvents and nonsolvents inorder to ensure that the phosphorus is chemically bonded to the polymerrather than physically intermixed therewith.

Although only a post-reaction technique is described hereinabove and inthe following examples, it should be apparent to one skilled in the artthat the -C-N-P linkage may be inserted in a substantially olefinpolymer by copolymerization or by postpolymerization employingcomonomers or polymers already containing the linkage.

EXAMPLE 1 Approximately 30 grams of an ethyleneacrylamide copolymer(melt index=l0) containing acrylamide was handed on a 2" diameter rubbermill at 125 C. until a melt was obtained following which 3 grams (36% ofstoichiometric based on amide) of benzene phosphinic dichloride wasadded to the melt. The temperature of the mill was raised to 180 C. andthe composition milled for 10 minutes. The polymer was then sheeted offthe mill. A compression molded bar of the resulting polymer wasself-extinguishing according to ASTM D-63556T and an infrared analysisof a thin film of the polymer indicated the presence of C-N-P linkage.The polymer contained pproximately 1.5% phosphorus 4 EXAMPLE 2Approximately 15 grams of an ethylenemethacrylyl chloride copolymer wasdissolved in 900 g. of water-free toluene at 72 C. in an enclosed glassvessel. After the addition of 75 g. of dry pyridine, 17 grams (340%stoichiometric) of diethyl phosphoramidate was added. The mixture wasstirred and heated to C. for 48 hours. After introducing sufficient drygaseous ammonia to react with any unreacted acid chloride remaining, thepolymer was precipitated in 3 liters of acetone, and the polymerisolated. A compression molded bar of the polymer was self-extinguishingwhen tested according to ASTM D-635-56T. An infrared analysis of a thinfilm of the polymer indicated the presence of the C-N--P linkage.

The flame-resistant compositions prepared by means of this invention areuseful in any application employing similar but nonflame-resistantresins. These applications include uses as shaped structures such as afilm, fiber, tubing, wire coating, rod stock and a cellular or foamedstructure. For example, a flame-resistant extrudate from the orifice ofa melt indexer, while still molten, is drawn into a fiber having goodflexibility and toughness. When a suitable mandrel is positioned at theorifice of the melt indexer, the extrudate is shaped into tubing orpipe, also, having good flexibility and toughness. A sample of aflameresistant resin as prepared herein is compression molded betweenplatens for one minute at C. and 30,000 p.s.i. to give a transparentfilm which is useful as a wrapping or protective cover. A similar samplewhich contains 0.75% of an azodicarbonamide blowing agent is extrudedthrough a melt indexer at 200 C. to yield a compressible cellularstructure having utility as a packaging cushion. When a 0.025-inchcopper wire is drawn through a molten sample of a flame-resistant resinas prepared herein, it is provided with a protective insulation whichadheres to the wire despite extended flexing. Still another sample isinjection molded from a conventional injection molding machine at 230 C.into the cavity of a cool mold to produce a flameresistant, molded,shapedstructure.

I claim:

1. A flame-resistant composition comprising a high molecular weight,normally solid, substantially olefinic hydrocarbon copolymer, saidcopolymer containing at least 87 mole percent bound mono-a-olefinichydrocarbon and a bound monoethylenically unsaturated comonomer havingpendent functional groups capable of being reduced to an acid halide oramide and having the group C-NP substantially uniformly dispersedtherethrough with the carbon atom of said -C-NP group being chemicallybonded to the main chain of said polymer through an uninterruptedcarbon-carbon linkage at the site of said functional group, saidcomposition having from one P atom per 1000 carbon atoms to 4 molepercent of P atoms based upon the monomer units in said copolymer.

2. The composition of claim 1 wherein the maximum amount of the bound Patom is 2.5 mole percent based upon the monomer units in saidsubstantially olefinic hydrocarbon polymer.

3. The composition of claim 2 wherein said substantially oleglnichydrocarbon polymer is ethylene and methacrylic ac1 4. The compositionof claim 1 in the form of a shaped structure.

5. The composition of claim 3 wherein the shaped structure is selectedfrom the group consisting of a film, tube, fiber, rod and an expandedcellular structure.

6. A flame-resistant composition comprising a high molecular weight,normally solid, substantially olefinic hydrocarbon copolymer containing(a) at least 87 mole percent bound mono-a-olefinic hydrocarbon havingthe structure CH =CHR wherein R is selected from t e group consisting ofhydrogen and alkyl radicals having 1 to 18 carbon atoms, and (b) a boundmonoethylenically unsaturated comonomer selected from the groupconsisting of alkenoic acids, alkenedioic acids, alkenetricarboxylicacids, and methylene alkanedioic acids, each of said acids having 3 to18 carbon atoms and alkenyl amides having 2 to 20 carbon atoms andcombinations thereof, said flame-resistant composition containing thegroup -CN-P, substantially uniformly dispersed therethrough, with thecarbon atom of said group being chemically bonded to the main chain ofsaid substantially hydrocarbon copolymer through an uninterruptedcarboncarbon linkage at the site of said functional groups of saidmonoethylenically unsaturated comonomer, said flame-resistantcomposition having a content of from one P atom per 1000 carbon atoms to15 Weight percent of said substantially hydrocarbon copolymer.

References Cited UNITED STATES PATENTS 3,267,113 8/1966 Carboni 260-88.1

JOSEPH L. SCHOFER, Primary Examiner.

M. B. KURTZMAN, Assistant Examiner.

US. Cl. X.R. 26045.9, 78.5

